[Monetdb-developers] bat.new undefined

Martin Kersten Martin.Kersten at cwi.nl
Thu Nov 15 09:55:33 CET 2007


Fabian Groffen wrote:
> On 14-11-2007 22:56:27 +0100, Martin Kersten wrote:
>> Fabian Groffen wrote:
>>> On 14-11-2007 22:46:34 +0100, darabi at web.de wrote:
>>>   
>>>> mal>    # create schema, if it doesn't exist
>>>> mal>    catch MALException:str;
>>>> mal>
>>>> mal>        s := bat.new(:void,:oid);
>>>> mal>        bat.setName(s, "schema");
>>>> mal>        bat.setPersistent(s);
>>>> mal>
>>>> mal>        s := bat.new(:void,:void);
>>>>     
>>> The error occurs here.  This is a typing issue, but the expert has to
>>> give his opinion on it to make it final.  ;)
>>>
>>> You can try (haven't tested it) to first set it to nil, e.g.:
>>> s := nil;
>>>   
>> there he is:-)
>>
>> In MAL arguments and signatures are strongly typed.
>>
>> s:bat[:void,:oid] := bat.new(_6:void, _6:void)
>>
>> is type incompatible.
>> it should have been
>>
>> s:bat[:void,:oid] := bat.new(_6:void, _7:oid)
> 
> The observation is that you cannot reuse variables, unless you want to
> reuse them for something which has exactly the same type.  The
> assignment makes that counter intuitive, because it /does/ work when the
> variable has never been referenced before.
> 
The orginal example showed that the variable was already declared, i.e.
type was frozen.
mal>        s := bat.new(:void,:oid);
mal>        bat.setName(s, "schema");
mal>        bat.setPersistent(s);
mal>
mal>        s := bat.new(:void,:void);
mal>        bat.setName(s, "version");
mal>        bat.setPersistent(s);
mal>
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